Divalent cations modulate the transient outward current in rat ventricular myocytes.

Area of Science:

• Cardiovascular Physiology
• Neuroscience
• Ion Channel Modulation

Background:

• The transient outward potassium current (Ito) plays a crucial role in cardiac action potential repolarization.
• Understanding the regulation of Ito is essential for comprehending cardiac electrophysiology and potential therapeutic targets.

Purpose of the Study:

• To investigate the effects of various divalent cations on the modulation of the transient outward potassium current (Ito).
• To elucidate the specific mechanisms by which divalent cations influence the voltage dependence and kinetics of Ito.

Main Methods:

• Whole-cell patch-clamp technique applied to enzymatically isolated rat ventricular myocytes.
• Application of different concentrations of divalent cations including Cd2+, Co2+, Ni2+, Ca2+, Cu2+, and Zn2+.
• Analysis of voltage-dependent activation and inactivation properties, as well as activation and inactivation kinetics of Ito.

Main Results:

• 1 mM Cd2+ suppressed Ito at negative potentials (< -70 mV) and augmented it at positive potentials (> -50 mV).
• Divalent cations induced rightward shifts in the voltage dependence of Ito activation and inactivation, altering current kinetics.
• Potent effects were observed with micromolar concentrations of Cu2+ and Zn2+, and similar findings were noted in hippocampal neurons.

Conclusions:

• Divalent cations exert significant and specific modulatory effects on the voltage dependence and kinetics of the transient outward potassium current (Ito).
• These cations may function as endogenous regulators of Ito, particularly in cells with resting potentials more positive than -60 mV.
• The findings highlight the potential for targeted ion modulation in controlling cellular excitability.